264 research outputs found
A new beamline for laser spin-polarization at ISOLDE
A beamline dedicated to the production of laser-polarized radioactive beams
has been constructed at ISOLDE, CERN. We present here different simulations
leading to the design and construction of the setup, as well as technical
details of the full setup and examples of the achieved polarizations for
several radioisotopes. Beamline simulations show a good transmission through
the entire line, in agreement with observations. Simulations of the induced
nuclear spin-polarization as a function of atom-laser interaction length are
presented for Na, [1] and for Ar, which is studied in this
work. Adiabatic spin rotation of the spin-polarized ensemble of atoms, and how
this influences the observed nuclear ensemble polarization, are also performed
for the same nuclei. For Ar, we show that multiple-frequency pumping
enhances the ensemble polarization by a factor 1.85, in agreement with
predictions from a rate equations model.
[1] J. Phys. G: Nucl. Part. Phys./174408400
A multi-reflection time-of-flight mass spectrometer for the offline ion source of the PUMA experiment
The antiProton Unstable Matter Annihilation experiment (PUMA) at CERN aims at
investigating the nucleon composition in the matter density tail of radioactive
as well as stable isotopes by use of low-energy antiproton-nucleon annihilation
processes. For this purpose, antiprotons provided by the Extra Low ENergy
Antiproton (ELENA) facility will be trapped together with the ions of interest.
While exotic ions will be obtained by the Isotope mass Separator On-Line DEvice
(ISOLDE), stable ions will be delivered from an offline ion source setup
designed for this purpose. This allows the proposed technique to be applied to
a variety of stable nuclei and for reference measurements. For beam
purification, the ion source setup includes a multi-reflection time-of-flight
mass spectrometer (MR-ToF MS). Supported by SIMION simulations, an earlier
MR-ToF MS design has been modified to meet the requirements of PUMA. During
commissioning of the new MR-ToF device with Ar ions, mass resolving powers
in excess of 50,000 have been obtained after 150 revolutions, limited by the
chopping of the continuous beam from an electron impact ionisation source
Precision Mass Measurements of 129-131Cd and Their Impact on Stellar Nucleosynthesis via the Rapid Neutron Capture Process
Masses adjacent to the classical waiting-point nuclide 130Cd have been
measured by using the Penning- trap spectrometer ISOLTRAP at ISOLDE/CERN. We
find a significant deviation of over 400 keV from earlier values evaluated by
using nuclear beta-decay data. The new measurements show the reduction of the N
= 82 shell gap below the doubly magic 132Sn. The nucleosynthesis associated
with the ejected wind from type-II supernovae as well as from compact object
binary mergers is studied, by using state-of-the-art hydrodynamic simulations.
We find a consistent and direct impact of the newly measured masses on the
calculated abundances in the A = 128 - 132 region and a reduction of the
uncertainties from the precision mass input data
Probing the N = 32 shell closure below the magic proton number Z = 20: Mass measurements of the exotic isotopes 52,53K
The recently confirmed neutron-shell closure at N = 32 has been investigated
for the first time below the magic proton number Z = 20 with mass measurements
of the exotic isotopes 52,53K, the latter being the shortest-lived nuclide
investigated at the online mass spectrometer ISOLTRAP. The resulting
two-neutron separation energies reveal a 3 MeV shell gap at N = 32, slightly
lower than for 52Ca, highlighting the doubly-magic nature of this nuclide.
Skyrme-Hartree-Fock-Boguliubov and ab initio Gorkov-Green function calculations
are challenged by the new measurements but reproduce qualitatively the observed
shell effect.Comment: 5 pages, 5 figure
First Glimpse of the N= 82 Shell Closure below Z= 50 from Masses of Neutron-Rich Cadmium Isotopes and Isomers
We probe the N = 82 nuclear shell closure by mass measurements of neutron-rich cadmium isotopes with the ISOLTRAP spectrometer at ISOLDE-CERN. The new mass of 132 Cd offers the first value of the N = 82 , two-neutron shell gap below Z = 50 and confirms the phenomenon of mutually enhanced magicity at 132 Sn . Using the recently implemented phase-imaging ion-cyclotron-resonance method, the ordering of the low-lying isomers in 129 Cd and their energies are determined. The new experimental findings are used to test large-scale shell-model, mean-field, and beyond-mean-field calculations, as well as the ab initio valence-space in-medium similarity renormalization group
Isomeric excitation energy for In from mass spectrometry reveals constant trend next to doubly magic Sn
The excitation energy of the 1/2 isomer in In at is
measured to be 671(37) keV and the mass uncertainty of the 9/2 ground state
is significantly reduced using the ISOLTRAP mass spectrometer at ISOLDE/CERN.
The measurements exploit a major improvement in the resolution of the
multi-reflection time-of-flight mass spectrometer. The results reveal an
intriguing constancy of the isomer excitation energies in
neutron-deficient indium that persists down to the shell closure, even
when all neutrons are removed from the valence shell. This trend is used to
test large-scale shell model, \textit{ab initio}, and density functional theory
calculations. The models have difficulties describing both the isomer
excitation energies and ground-state electromagnetic moments along the indium
chain.Comment: 13 pages, 4 figure
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